Widely Controllable Syngas Production by a Dye-Sensitized TiO2 Hybrid System with ReI and CoIII Catalysts under Visible-Light Irradiation.

Visible-light irradiation of a ternary hybrid catalyst prepared by grafting a dye, an H2 evolving CoIII catalyst and a CO-producing ReI catalyst on TiO2 have been found to produce both H2 and CO (syngas) in CO2 -saturated N,N-dimethyl formamide (DMF)/water solution containing a 0.1 m sacrificial electron donor. The H2 /CO ratios are effectively controlled by changing either the water content of the solvent or the molar ratio of the ReI and CoIII catalysts ranging from 1:2 to 15:1. The controlled syngas formation is discussed in terms of competitive electron flow from TiO2 to each of the CO2 -reduction and hydrogen-evolving sites depending on the efficiencies of the two catalytic reaction cycles under given reaction conditions.